Project Summary/Abstract Chronic pain of the body and orofacial region represents a major health burden and the neural circuit mechanisms underlying long-lasting pain remain largely unknown. The current treatment options for pain are largely non-specific, have unwanted side effects, poor efficacy in many patients, and some have abuse potential. Therefore, the need to design more targeted therapies is imperative and to accomplish this, knowledge of the neural circuits responsible for pain is critical. The long-term objectives of this research are to define neural circuit mechanisms responsible for chronic pain, particularly in the orofacial region. The principal investigator has made use of a new mouse line in which he can target blue-light sensitive ion channels to molecular populations of nociceptors and optogenetically activate them in vivo. His preliminary data shows that he can trigger long-lasting spontaneous pain with this novel and non-invasive technique. He has also shown that he can use similar technologies with the Cre-lox system to ablate molecularly defined populations of nociceptors to investigate their functions in pain. In Aim 1 of the K99 mentored phase he will use optogenetics coupled with animal behavior and electrophysiology to uncover neural circuit mechanisms important for the transition from acute to chronic pain. In Aim 2 of the K99 mentored phase he will use a tooth pulp injury model with an apparatus to measure orofacial pain coupled with ablation or activation of a molecularly defined population of nociceptors to determine their functions in dental pain. Lastly, during the R00 independent phase in Aim 3, the principal investigator will use the the same tooth pulp injury model together with the skills and techniques acquired during the mentored phase to investigate two additional populations of nociceptors that may be involved in sensitivity to thermal stimuli following dental pulp injury. Completion of the three listed aims will make him proficient in using mouse molecular genetics to control the activity of nociceptors while investigating their functions in dental pain. The principal investigator will learn the skills and new techniques necessary to accomplish the proposed research under the guidance of his mentoring team (Drs. Brian Schmidt, Wenqin Luo, Minghong Ma, Michael Nusbaum, and Jonathan Raper) and his consultants (Drs. Elliot Hersh, and Syngcuk Kim, and Yuanxiang Tao), who have pioneering expertise in using the listed methods and models. Importantly, his mentoring committee collectively has a very strong track record of training postdoctoral fellows in transitioning into independent investigators. He will also engage in seminars and take coursework on modern neuroscience techniques, grant writing, bioethics training, and training on running a laboratory. Combining the new skills learned during the K99 mentored phase with his prior expertise in molecular biology and mouse genetic targeting, will ensure a strong technical foundation to launch an independent laboratory dissecting neural circuit mechanisms responsible for orofacial system pain, which are still very poorly defined.